Advertisement

Advertisement

Never-before-seen galaxy spotted orbiting the Milky Way

ESO/APEX/ATLASGAL consortium/NASA/GLIMPSE consortium/ESA/Planck

THE galaxy’s empire has a new colony – a dwarf galaxy larger than nearly all the other satellites of the Milky Way.

About four dozen known galaxies orbit our own. Now, Gabriel Torrealba at the University of Cambridge and his colleagues have found a new galaxy about 380,000 light years away in the Crater constellation. “It’s the fourth largest satellite of the Milky Way,” Torrealba says.

Advertisement

Named the Crater 2 dwarf, the new galaxy is not apparent to human eyes as its stars are so spread out, although some stars within it are visible. The team were only able to find it this January by using a computer to look for unusually dense clumps of stars in data from images taken by a telescope in Chile.

Most galaxies don’t have defined edges, so astronomers sometimes express a galaxy’s size in terms of its “half-light diameter”, which encloses the brightest part of the galaxy and emits half of its light. The Crater 2 dwarf has a half-light diameter of 7000 light years – which, if we could see it, would look twice as big as the full moon (arxiv.org/abs/1601.07178).

This article appeared in print under the headline “Wispy dwarf in Milky Way’s thrall”